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Main
Date: 23 Sep 2006 02:58:39
From: Spokes
Subject: Stray asteroids from other systems or galaxies out there?
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I'm new to this NG. One thing that I've often wondered about is the
possibility of a stray asteroid entering our system or even hitting our
planet.
Do asteroids from other systems or galaxies come our way? Is is
possible or common? Any examples?
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Date: 23 Sep 2006 09:14:25
From: Greg Neill
Subject: Re: Stray asteroids from other systems or galaxies out there?
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"Spokes" <spokesman123@hotmail.com > wrote in message
news:1159005519.743820.250130@k70g2000cwa.googlegroups.com...
> I'm new to this NG. One thing that I've often wondered about is the
> possibility of a stray asteroid entering our system or even hitting our
> planet.
> Do asteroids from other systems or galaxies come our way? Is is
> possible or common? Any examples?
>
It would probably be difficult to tell the difference
between an object perturbed in from the Oort cloud and
one that has an extra-solarsystem origin. But there's
no reason why bits from other solar systems shouldn't
manage to scatter here and there.
Getting hit by something from another galaxy is certainly
possible if unlikely. The gravitational well that an
asteroid would have to climb out of to escape its parent
galaxy would be formidable. An estimate would go as follows.
An asteroid at the periphery of a galaxy of, say,
200 billion sun masses and 100,000ly radius would have
an escape velocity of approximately
Vesc = sqrt(2GM/r)
(I say approximately because the mass distribution of
the galaxy may not be spherical)
Putting some numbers to this,
G = 6.67 x 10^-11 m^3 kg^-1 sec^-2
M = 200x10^9 x 2x10^30 kg = 4x10^41 kg
r = 100000ly = 9.46x10^17 km
Vesc = ~ 8.6 x 10^5 km/hr
Not an impossible speed for a massive body to attain
via near-miss stellar interactions. Of course, having
managed to escape the parent galaxy the object would
then have to find ours. This may not be too great a
problem for galaxies within our local group, as they
are gravitationally bound anyways. There's a *lot*
of empty space out there between galaxies, though.
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Date: 23 Sep 2006 11:42:24
From: Thomas Lee Elifritz
Subject: Re: Stray asteroids from other systems or galaxies out there?
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Greg Neill wrote:
> "Spokes" <spokesman123@hotmail.com> wrote in message
> news:1159005519.743820.250130@k70g2000cwa.googlegroups.com...
>> I'm new to this NG. One thing that I've often wondered about is the
>> possibility of a stray asteroid entering our system or even hitting our
>> planet.
>> Do asteroids from other systems or galaxies come our way? Is is
>> possible or common? Any examples?
>>
>
> It would probably be difficult to tell the difference
> between an object perturbed in from the Oort cloud and
> one that has an extra-solarsystem origin.
Actually, it's pretty easy, we do it all the time - isotope ratios.
http://cosmic.lifeform.org
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Date: 23 Sep 2006 14:26:20
From: Greg Neill
Subject: Re: Stray asteroids from other systems or galaxies out there?
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"Thomas Lee Elifritz" <cosmic@lifeform.org > wrote in message
news:oudRg.1549$QF6.1005@newsfe02.lga...
> Greg Neill wrote:
> > "Spokes" <spokesman123@hotmail.com> wrote in message
> > news:1159005519.743820.250130@k70g2000cwa.googlegroups.com...
> >> I'm new to this NG. One thing that I've often wondered about is the
> >> possibility of a stray asteroid entering our system or even hitting our
> >> planet.
> >> Do asteroids from other systems or galaxies come our way? Is is
> >> possible or common? Any examples?
> >>
> >
> > It would probably be difficult to tell the difference
> > between an object perturbed in from the Oort cloud and
> > one that has an extra-solarsystem origin.
>
> Actually, it's pretty easy, we do it all the time - isotope ratios.
Isotope rations would only give the age of the body since
last melting. Granted, if the Oort bodies all turn out
to have the same "setting" of their clocks, then something
older would be evidence of extra-solar system origin.
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Date: 24 Sep 2006 11:42:33
From: Paul Schlyter
Subject: Re: Stray asteroids from other systems or galaxies out there?
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In article <45153180$0$24198$9a6e19ea@news.newshosting.com >,
Greg Neill <gneillREM@OVEnetcom.ca > wrote:
> "Spokes" <spokesman123@hotmail.com> wrote in message
> news:1159005519.743820.250130@k70g2000cwa.googlegroups.com...
>> I'm new to this NG. One thing that I've often wondered about is the
>> possibility of a stray asteroid entering our system or even hitting our
>> planet.
>> Do asteroids from other systems or galaxies come our way? Is is
>> possible or common? Any examples?
>
> It would probably be difficult to tell the difference
> between an object perturbed in from the Oort cloud and
> one that has an extra-solarsystem origin.
In most such cases, it wouldn't be very difficult. A body from
another solar system would approach the Sun with a velocity of
probably at least several km/s, and would in our solar system follow
an orbit which would be significantly hyperbolic. No such body has
ever been observed.
> But there's
> no reason why bits from other solar systems shouldn't
> manage to scatter here and there.
>
> Getting hit by something from another galaxy is certainly
> possible if unlikely. The gravitational well that an
> asteroid would have to climb out of to escape its parent
> galaxy would be formidable. An estimate would go as follows.
>
> An asteroid at the periphery of a galaxy of, say,
> 200 billion sun masses and 100,000ly radius would have
> an escape velocity of approximately
>
> Vesc = sqrt(2GM/r)
>
> (I say approximately because the mass distribution of
> the galaxy may not be spherical)
>
> Putting some numbers to this,
>
> G = 6.67 x 10^-11 m^3 kg^-1 sec^-2
> M = 200x10^9 x 2x10^30 kg = 4x10^41 kg
> r = 100000ly = 9.46x10^17 km
>
> Vesc = ~ 8.6 x 10^5 km/hr
...which corresponds to 240 km/s....
And that asteroid would also need a quite large excess velocity about
that - to be able to travel from M31 to our galaxy within the
lifetime of our universe, an asteroid would need a mean velocity of
some 100 km/s.
A body which escaped from another galaxy, entered our own galaxy and
then our solar system, would thus do so at a very high velocity, and
would follow a path which essentially would be a straight line
through our solar system, curved only a little bit closest to the Sun.
> Not an impossible speed for a massive body to attain
> via near-miss stellar interactions. Of course, having
> managed to escape the parent galaxy the object would
> then have to find ours. This may not be too great a
> problem for galaxies within our local group, as they
> are gravitationally bound anyways. There's a *lot*
> of empty space out there between galaxies, though.
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
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Date: 25 Sep 2006 18:27:07
From: Chris L Peterson
Subject: Re: Stray asteroids from other systems or galaxies out there?
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On Sun, 24 Sep 2006 11:42:33 GMT, pausch@saaf.se (Paul Schlyter) wrote:
>In most such cases, it wouldn't be very difficult. A body from
>another solar system would approach the Sun with a velocity of
>probably at least several km/s, and would in our solar system follow
>an orbit which would be significantly hyperbolic. No such body has
>ever been observed.
The mass density of Solar System bodies follows a power law
distribution: there are many more small objects than large. It is
reasonable to assume that this would hold also for any objects with an
origin outside our system. To some extent this is observed: microscopic
grains from other systems have certainly been found.
So for every body large enough to be observed in space and have its
orbit calculated, there ought to be many that could hit the Earth and
never be seen as anything other than meteors (which rarely have their
parent orbits determined). Obviously such meteors will be rare compared
with ordinary meteors of local origin, and no meteorite has ever been
recovered that has its origin in another star system. But it seems
perfectly possible for such objects to make it here, just statistically
unlikely. (And far, far less likely from another galaxy.)
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 26 Sep 2006 09:49:45
From: Michael
Subject: Re: Stray asteroids from other systems or galaxies out there?
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On Sun, 24 Sep 2006 11:42:33 GMT, pausch@saaf.se (Paul Schlyter), wrote
the following in sci.astro.amateur:
> > Vesc = ~ 8.6 x 10^5 km/hr
>
> ...which corresponds to 240 km/s....
Not to nitpick, but might you be one decimal place off? I'm thinking
that 8.6 x 10^5 km/hr = a little under 24 km/s.
> And that asteroid would also need a quite large excess velocity about
> that - to be able to travel from M31 to our galaxy within the lifetime of
> our universe, an asteroid would need a mean velocity of some 100 km/s.
Just ballpark figures, but at slightly over 2 million light years from
our galaxy to M31, that's around 2 x 10^19 km. (I'm going from memory
here, but I think the distance to M31 is usually given as around 2.2
million l.y..)
At your figure of 100 km/s, the asteroid could cover that distance in a
mere 6 billion years, give or take a little.
I like to think that the universe will hang around quite a bit longer
than that. I mean, a Hostess Twinkie is presumably good for nearly 3
billion years, and I have to believe that the universe enjoys more than
twice the life expectancy of a Twinkie, difficult as it may be for one
to emotionally grasp just how long "longer than a Twinkie's good for"
truly is.
--
Michael
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Date: 26 Sep 2006 09:48:51
From: Brian Tung
Subject: Re: Stray asteroids from other systems or galaxies out there?
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Michael wrote:
> Not to nitpick, but might you be one decimal place off? I'm thinking
> that 8.6 x 10^5 km/hr = a little under 24 km/s.
Why do you think that? 8.6 x 10^5 = 860,000 and if you divide that by
3,600 you get about 240.
> Just ballpark figures, but at slightly over 2 million light years from
> our galaxy to M31, that's around 2 x 10^19 km. (I'm going from memory
> here, but I think the distance to M31 is usually given as around 2.2
> million l.y..)
It's bounced around a little, with figures as high as 2.9 Mly, but I
think the best current figure is 2.5 Mly. Still, that means that an
asteroid going at 100 km/s could cover the distance in 7.5 billion
years, a little more than half the universe's lifetime.
One potential problem is that a typical asteroid won't be heading in the
"right" direction. We can detect asteroids at distances up to maybe 50
AU--bigger ones further away, smaller ones only closer in. That's a
cross-section of 100 AU, which as seen from M31's distance subtends just
a mere eighth of a milli-arcsecond. As a result, out of every 10^20
asteroids that leave M31, barely one gets close enough to be detected.
So, if M31 ejects asteroids at the rate of about 10 billion per year,
then it's about even money whether any of them have passed through.
(Maybe a little lower, since it's taken a while for stellar metallicity
to get high enough to create asteroids in the first place.) If it's
slower than that, chances are it hasn't happened, and if it's faster
than that, it probably has--but who knows how easy they would be to
catch.
--
Brian Tung <brian@isi.edu >
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html
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Date: 23 Sep 2006 11:46:58
From: Johnny Borborigmi
Subject: Re: Stray asteroids from other systems or galaxies out there?
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On 2006-09-23 05:58:39 -0400, "Spokes" <spokesman123@hotmail.com > said:
> I'm new to this NG. One thing that I've often wondered about is the
> possibility of a stray asteroid entering our system or even hitting our
> planet.
> Do asteroids from other systems or galaxies come our way? Is is
> possible or common? Any examples?
No examples as far as I know. Possible? I'm not sure myself.
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Date: 23 Sep 2006 18:05:32
From:
Subject: Re: Stray asteroids from other systems or galaxies out there?
|
Spokes wrote:
> Do asteroids from other systems or galaxies come our way? Is is
> possible or common? Any examples?
It is certainly possible. Stars sometimes pass very close to each other
(though very rarely), and the solar systems of such stars will be
disrupted when such approaches occur, with some objects expelled from
the systems. So there are probably countless vagabond objects, small
and large, drifting about between the stars.
A weird doomsday scenario that I have never heard anyone mention would
be for a large rogue object, say something the size of Neptune, or
larger, to pass through the inner Solar System and quietly alter the
eccentricity of Earth's orbit.
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Date: 24 Sep 2006 11:42:33
From: Paul Schlyter
Subject: Re: Stray asteroids from other systems or galaxies out there?
|
In article <1159059932.320249.146990@m73g2000cwd.googlegroups.com >,
<allisonki@IGNmail.com > wrote:
> Spokes wrote:
>> Do asteroids from other systems or galaxies come our way? Is is
>> possible or common? Any examples?
>
> It is certainly possible. Stars sometimes pass very close to each other
> (though very rarely), and the solar systems of such stars will be
> disrupted when such approaches occur, with some objects expelled from
> the systems. So there are probably countless vagabond objects, small
> and large, drifting about between the stars.
>
> A weird doomsday scenario that I have never heard anyone mention would
> be for a large rogue object, say something the size of Neptune, or
> larger, to pass through the inner Solar System and quietly alter the
> eccentricity of Earth's orbit.
Such an event would probably alter the semimajor axis and the inclination
of the Earth's orbit too..... anyway, there has been such novels:
You should read Robert Heinlein's "The Fifth Planet" ......
In Sweden we had an astronomer, Peter Nilson, who later became a writer
and wrote a dozen novels. One of them was a two-part science fiction
novel "The Space Guard"/"Nyaga" (don't know if there's any translation
to English though), where he envisions a future where theology has
become an exact science, and where the most powerful computers (quantum
computers of course) are used to run simulations of God ..... anyway,
in that novel, suddenly a black hole turns up on a collision course
with the solar system, and more and more of the stars in the sky just
appear to vanish.....
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
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Date: 24 Sep 2006 08:22:37
From: Starlord
Subject: Re: Stray asteroids from other systems or galaxies out there?
|
How about the Sci-Fi book (made into a movie) When Worlds Collide?
--
The Lone Sidewalk Astronomer of Rosamond
Telescope Buyers FAQ
http://home.inreach.com/starlord
Sidewalk Astronomy
www.sidewalkastronomy.info
The Church of Eternity
http://home.inreach.com/starlord/church/Eternity.html
"Paul Schlyter" <pausch@saaf.se > wrote in message
news:ef5q6i$1pqf$1@merope.saaf.se...
> In article <1159059932.320249.146990@m73g2000cwd.googlegroups.com>,
> <allisonki@IGNmail.com> wrote:
>
>> Spokes wrote:
>>> Do asteroids from other systems or galaxies come our way? Is is
>>> possible or common? Any examples?
>>
>> It is certainly possible. Stars sometimes pass very close to each other
>> (though very rarely), and the solar systems of such stars will be
>> disrupted when such approaches occur, with some objects expelled from
>> the systems. So there are probably countless vagabond objects, small
>> and large, drifting about between the stars.
>>
>> A weird doomsday scenario that I have never heard anyone mention would
>> be for a large rogue object, say something the size of Neptune, or
>> larger, to pass through the inner Solar System and quietly alter the
>> eccentricity of Earth's orbit.
>
> Such an event would probably alter the semimajor axis and the inclination
> of the Earth's orbit too..... anyway, there has been such novels:
>
> You should read Robert Heinlein's "The Fifth Planet" ......
>
> In Sweden we had an astronomer, Peter Nilson, who later became a writer
> and wrote a dozen novels. One of them was a two-part science fiction
> novel "The Space Guard"/"Nyaga" (don't know if there's any translation
> to English though), where he envisions a future where theology has
> become an exact science, and where the most powerful computers (quantum
> computers of course) are used to run simulations of God ..... anyway,
> in that novel, suddenly a black hole turns up on a collision course
> with the solar system, and more and more of the stars in the sky just
> appear to vanish.....
>
> --
> ----------------------------------------------------------------
> Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
> e-mail: pausch at stockholm dot bostream dot se
> WWW: http://stjarnhimlen.se/
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Date: 26 Sep 2006 05:39:28
From: William Hamblen
Subject: Re: Stray asteroids from other systems or galaxies out there?
|
On 2006-09-24, Starlord <starlord@sidewalkastronomy.info > wrote:
> How about the Sci-Fi book (made into a movie) When Worlds Collide?
And "After Worlds Collide".
Bud
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Date: 23 Sep 2006 12:24:42
From: Greg Crinklaw
Subject: Re: Stray asteroids from other systems or galaxies out there?
|
Spokes wrote:
> I'm new to this NG. One thing that I've often wondered about is the
> possibility of a stray asteroid entering our system or even hitting our
> planet.
> Do asteroids from other systems or galaxies come our way? Is is
> possible or common? Any examples?
To date no interstellar objects have been observed in the inner solar
system, based on their orbits.
Clear skies,
Greg
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)
SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html
To reply take out your eye
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Date: 23 Sep 2006 13:35:42
From: Shawn Curry
Subject: Re: Stray asteroids from other systems or galaxies out there?
|
Greg Crinklaw wrote:
> Spokes wrote:
>
>> I'm new to this NG. One thing that I've often wondered about is the
>> possibility of a stray asteroid entering our system or even hitting our
>> planet.
>> Do asteroids from other systems or galaxies come our way? Is is
>> possible or common? Any examples?
>
>
> To date no interstellar objects have been observed in the inner solar
> system, based on their orbits.
Not even comets? Thought some have been shown to have enough velocity
to leave the solar system. Are these (if I'm correct) assumed to be
Oort cloud objects? Do spectra confirm a similar origin?
Shawn
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Date: 23 Sep 2006 16:03:59
From: Greg Crinklaw
Subject: Re: Stray asteroids from other systems or galaxies out there?
|
Shawn Curry wrote:
> Greg Crinklaw wrote:
>> Spokes wrote:
>>
>>> I'm new to this NG. One thing that I've often wondered about is the
>>> possibility of a stray asteroid entering our system or even hitting our
>>> planet.
>>> Do asteroids from other systems or galaxies come our way? Is is
>>> possible or common? Any examples?
>>
>>
>> To date no interstellar objects have been observed in the inner solar
>> system, based on their orbits.
>
> Not even comets? Thought some have been shown to have enough velocity
> to leave the solar system. Are these (if I'm correct) assumed to be
> Oort cloud objects? Do spectra confirm a similar origin?
All comets with known orbits originated in the Oort Cloud, which is an
orbit distinct from that of an interloper. I'm not sure that the
spectra of comets could be reliably used to determine their origin.
Clear skies,
Greg
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)
SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html
To reply take out your eye
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Date: 23 Sep 2006 18:18:28
From: Shawn Curry
Subject: Re: Stray asteroids from other systems or galaxies out there?
|
Greg Crinklaw wrote:
> Shawn Curry wrote:
>
>> Greg Crinklaw wrote:
>>
>>> Spokes wrote:
>>>
>>>> I'm new to this NG. One thing that I've often wondered about is the
>>>> possibility of a stray asteroid entering our system or even hitting our
>>>> planet.
>>>> Do asteroids from other systems or galaxies come our way? Is is
>>>> possible or common? Any examples?
>>>
>>>
>>>
>>> To date no interstellar objects have been observed in the inner solar
>>> system, based on their orbits.
>>
>>
>> Not even comets? Thought some have been shown to have enough velocity
>> to leave the solar system. Are these (if I'm correct) assumed to be
>> Oort cloud objects? Do spectra confirm a similar origin?
>
>
> All comets with known orbits originated in the Oort Cloud, which is an
> orbit distinct from that of an interloper. I'm not sure that the
> spectra of comets could be reliably used to determine their origin.
The only reason I asked about spectra is that something with a really
long orbit and really unique spectrum would be interesting.
Shawn
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Date: 23 Sep 2006 19:50:24
From: Thomas Lee Elifritz
Subject: Re: Stray asteroids from other systems or galaxies out there?
|
Shawn Curry wrote:
> Greg Crinklaw wrote:
>> Shawn Curry wrote:
>>
>>> Greg Crinklaw wrote:
>>>
>>>> Spokes wrote:
>>>>
>>>>> I'm new to this NG. One thing that I've often wondered about is the
>>>>> possibility of a stray asteroid entering our system or even hitting
>>>>> our
>>>>> planet.
>>>>> Do asteroids from other systems or galaxies come our way? Is is
>>>>> possible or common? Any examples?
>>>>
>>>>
>>>>
>>>> To date no interstellar objects have been observed in the inner
>>>> solar system, based on their orbits.
>>>
>>>
>>> Not even comets? Thought some have been shown to have enough
>>> velocity to leave the solar system. Are these (if I'm correct)
>>> assumed to be Oort cloud objects? Do spectra confirm a similar origin?
>>
>>
>> All comets with known orbits originated in the Oort Cloud, which is an
>> orbit distinct from that of an interloper. I'm not sure that the
>> spectra of comets could be reliably used to determine their origin.
>
> The only reason I asked about spectra is that something with a really
> long orbit and really unique spectrum would be interesting.
All atoms are the same anywhere in the universe, it is the ratios of the
concentration of atoms in the primordial grains, as measured by their
isotope distributions, that determines whether those grains originated
in our particular solar nebula, or some other star's solar nebula.
Scattering, collisional, accretion and differentiation then effectively
homogenizes those grains, yielding the isotope ratios we know and love.
To determine that an entire solar system body is composed of mostly
extrasolar grains, in other words, to determine that a body had its
condensation and accretion occur within some other star's solar nebula,
derived from entirely different supernovae remnants, and then migrated
somehow to our solar system to be scattered and captured here, would
require in-situ analysis. It simply cannot be done by spectroscopy with
our currently available technological sophistication, assuming the solar
system body would be far out in the outer reaches of our solar system.
That being said, comets with hyperbolic orbits may be good candidates
for extrasolar bodies. Certainly extrasolar grains have been detected.
From : http://en.wikipedia.org/wiki/Comet
"Modern observations have revealed a few genuinely hyperbolic orbits,
but no more than could be accounted for by perturbations from Jupiter.
If comets pervaded interstellar space, they would be moving with
velocities of the same order as the relative velocities of stars near
the Sun (a few tens of kilometres per second). If such objects entered
the solar system, they would have positive total energies, and would be
observed to have genuinely hyperbolic orbits. A rough calculation shows
that there might be 4 hyperbolic comets per century, within Jupiter's
orbit, give or take one and perhaps two orders of magnitude."
I hope that helps. Isotopic analysis of solar grains is an active area
of research, if you are interested in that sort of thing, and there are
plenty of meteorites on the shelves, and more being found every day.
http://cosmic.lifeform.org
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Date: 23 Sep 2006 15:45:01
From: Thomas Lee Elifritz
Subject: Re: Stray asteroids from other systems or galaxies out there?
|
Shawn Curry wrote:
> Greg Crinklaw wrote:
>> Spokes wrote:
>>
>>> I'm new to this NG. One thing that I've often wondered about is the
>>> possibility of a stray asteroid entering our system or even hitting our
>>> planet.
>>> Do asteroids from other systems or galaxies come our way? Is is
>>> possible or common? Any examples?
>>
>>
>> To date no interstellar objects have been observed in the inner solar
>> system, based on their orbits.
>
> Not even comets? Thought some have been shown to have enough velocity
> to leave the solar system. Are these (if I'm correct) assumed to be
> Oort cloud objects? Do spectra confirm a similar origin?
We can only identify interstellar grains by isotope ratios. One would
have to sample the parent body, but surely most of these bodies would be
contaminated with extrasolar grains anyways. The question is how much of
this foreign material has migrated in from abroad, to our now fully
formed solar system, a system born from many supernovae remnants.
From examining meteorites and cosmic grains, we are now starting to get
an idea of what that environment was, and how it evolved over time.
To extend that analysis, we would have to start sampling far and wide.
It is highly unlikely that we would be able to carry out such an
analysis remotely, by spectroscopy. It would require local probes.
http://cosmic.lifeform.org
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Date: 25 Sep 2006 12:56:25
From: William C. Keel
Subject: Re: Stray asteroids from other systems or galaxies out there?
|
Greg Crinklaw <theskyhoundyoureye@yahoo.com > wrote:
> Spokes wrote:
>> I'm new to this NG. One thing that I've often wondered about is the
>> possibility of a stray asteroid entering our system or even hitting our
>> planet.
>> Do asteroids from other systems or galaxies come our way? Is is
>> possible or common? Any examples?
> To date no interstellar objects have been observed in the inner solar
> system, based on their orbits.
> Clear skies,
> Greg
Quibble: I've seen reports that radar estimates of the orbits of
large dust particles (0.1-0.25 microns size) show a small population
in distinctly hyperbolic orbits, which fits with the "interstellar"
dust gathering piece of the Stardust mission. Not very big, but the
only extra-solar-system origin objects yet identified beyond
cosmic-ray particles. There was even a suggestion that their
arrival directions implicated the dust disk around Beta Pic as
an important single source. And pleazzze, nobody suggest that the
IAU needs to have a commission address how large a dust grain needs
to be to qualify as a small solar-system body (bad enough that
orbit computations may now reveal things to be PHSSSB's).
Bill Keel
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Date: 25 Sep 2006 17:11:57
From: Thomas Lee Elifritz
Subject: Re: Stray asteroids from other systems or galaxies out there?
|
William C. Keel wrote:
> Greg Crinklaw <theskyhoundyoureye@yahoo.com> wrote:
>> Spokes wrote:
>>> I'm new to this NG. One thing that I've often wondered about is the
>>> possibility of a stray asteroid entering our system or even hitting our
>>> planet.
>>> Do asteroids from other systems or galaxies come our way? Is is
>>> possible or common? Any examples?
>
>> To date no interstellar objects have been observed in the inner solar
>> system, based on their orbits.
>
>> Clear skies,
>> Greg
>
> Quibble: I've seen reports that radar estimates of the orbits of
> large dust particles (0.1-0.25 microns size) show a small population
> in distinctly hyperbolic orbits, which fits with the "interstellar"
> dust gathering piece of the Stardust mission. Not very big, but the
> only extra-solar-system origin objects yet identified beyond
> cosmic-ray particles. There was even a suggestion that their
> arrival directions implicated the dust disk around Beta Pic as
> an important single source. And pleazzze, nobody suggest that the
> IAU needs to have a commission address how large a dust grain needs
> to be to qualify as a small solar-system body (bad enough that
> orbit computations may now reveal things to be PHSSSB's).
The IAU doesn't bother themselves with astrophysics. It's just too
complicated for them. They prefer to observe nice, well behaved solar
systems like our own. All solar systems should be just like ours.
I mean really, asteroids whizzing around everywhere, quadrillions of
pluterinos, it's simply too messy, better to just ignore all that.
http://cosmic.lifeform.org
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Date: 26 Sep 2006 14:44:18
From: Jim Klein
Subject: Re: Stray asteroids from other systems or galaxies out there?
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"Spokes" <spokesman123@hotmail.com > wrote:
>I'm new to this NG. One thing that I've often wondered about is the
>possibility of a stray asteroid entering our system or even hitting our
>planet.
>Do asteroids from other systems or galaxies come our way? Is is
>possible or common? Any examples?
I guess it is possible that solid objects far enough away from a
supernova could be ejected at high speed and travel a very long way
and hit something. Of course if we are the target, our geese will be
pretty well cooked. Something traveling at a significant fraction of
the speed of light might not be detectable before someone looks at the
data and says " Oh S$%#"
James E. Klein
jameseklein@earthlink.net
Engineering Calculations
http://www.ecalculations.com
ecalculations@ecalculations.com
Engineering Calculations is the home of
the KDP-2 Optical Design Program
for Windows and (soon) MAC OSX
Free KDP-2 (DEMO) downloadable!
1-818-507-5706 (Voice and Fax)
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Date: 26 Sep 2006 14:59:50
From: Chris L Peterson
Subject: Re: Stray asteroids from other systems or galaxies out there?
|
On Tue, 26 Sep 2006 14:44:18 GMT, Jim Klein <jameseklein@earthlink.net >
wrote:
>I guess it is possible that solid objects far enough away from a
>supernova could be ejected at high speed and travel a very long way
>and hit something.
It might take that for something to make it here from another galaxy,
but not from another star system in our own galaxy. Plenty of locally
produced comets have had hyperbolic orbits, which means someday they
could end up at another star. An object like that need not be traveling
faster than a local comet, asteroid, or meteoroid.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 27 Sep 2006 00:27:14
From: Sjouke Burry
Subject: Re: Stray asteroids from other systems or galaxies out there?
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Chris L Peterson wrote:
> On Tue, 26 Sep 2006 14:44:18 GMT, Jim Klein <jameseklein@earthlink.net>
> wrote:
>
>
>>I guess it is possible that solid objects far enough away from a
>>supernova could be ejected at high speed and travel a very long way
>>and hit something.
>
>
> It might take that for something to make it here from another galaxy,
> but not from another star system in our own galaxy. Plenty of locally
> produced comets have had hyperbolic orbits, which means someday they
> could end up at another star. An object like that need not be traveling
> faster than a local comet, asteroid, or meteoroid.
>
> _________________________________________________
>
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
Any comet in a hyperbolic orbit travels faster then the
solar escape velocity, which is >50km/s at the earth
orbit(or something like that), and would hit earth
at that speed or higher.
Solar bodies do not hit at that speed.(or they would
escape in the first place).
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Date: 26 Sep 2006 22:55:13
From: Chris L Peterson
Subject: Re: Stray asteroids from other systems or galaxies out there?
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On Wed, 27 Sep 2006 00:27:14 +0200, Sjouke Burry
<burrynulnulfour@ppllaanneett.nnlll > wrote:
>Any comet in a hyperbolic orbit travels faster then the
>solar escape velocity, which is >50km/s at the earth
>orbit(or something like that), and would hit earth
>at that speed or higher.
>Solar bodies do not hit at that speed.(or they would
>escape in the first place).
You need to distinguish between the heliocentric and geocentric
velocities. A Solar System body in a retrograde orbit can encounter the
Earth with a velocity higher than the escape velocity of the Solar
System (at the Earth). For example, Leonid meteors strike the Earth at
72 km/s, even though the escape velocity of the Solar System at the
Earth is only 42 km/s (with respect to the Sun).
You also need to consider the distance of the body from the Sun. For an
object in the Kuiper belt, the escape velocity from the Solar System is
only a few km/s, which is easily achieved through a simple collision. It
seems likely that our Solar System is ejecting quite a bit of material
from the Kuiper belt and Oort cloud.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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